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boost_fusion/doc/html/fusion/sequence/intrinsic/metafunctions/empty.html

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Regenerating/reorganizing docs [SVN r40832]
2007-11-06 12:13:52 +00:00
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<div class="titlepage"><div><div><h5 class="title">
<a name="fusion.sequence.intrinsic.metafunctions.empty"></a><a href="empty.html" title="empty">empty</a></h5></div></div></div>
<a name="fusion.sequence.intrinsic.metafunctions.empty.description"></a><h6>
<a name="id506944"></a>
<a href="empty.html#fusion.sequence.intrinsic.metafunctions.empty.description">Description</a>
</h6>
<p>
Returns the result type of <a href="../functions/empty.html" title="empty"><tt class="computeroutput"><span class="identifier">empty</span></tt></a>.
</p>
<a name="fusion.sequence.intrinsic.metafunctions.empty.synopsis"></a><h6>
<a name="id506993"></a>
<a href="empty.html#fusion.sequence.intrinsic.metafunctions.empty.synopsis">Synopsis</a>
</h6>
<pre class="programlisting">
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Seq</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">empty</span>
<span class="special">{</span>
<span class="keyword">typedef</span> <span class="emphasis"><em>unspecified</em></span> <span class="identifier">type</span><span class="special">;</span>
<span class="special">};</span>
</pre>
<div class="table">
<a name="id507092"></a><p class="title"><b>Table<EFBFBD>1.21.<2E>Parameters</b></p>
<table class="table" summary="Parameters">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
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<p>
Parameter
</p>
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<p>
Requirement
</p>
</th>
<th>
<p>
Description
</p>
</th>
</tr></thead>
<tbody><tr>
<td>
<p>
<tt class="computeroutput"><span class="identifier">Seq</span></tt>
</p>
</td>
<td>
<p>
A model of <a href="../../concepts/forward_sequence.html" title="Forward
Sequence">Forward
Sequence</a>
</p>
</td>
<td>
<p>
Argument sequence
</p>
</td>
</tr></tbody>
</table>
</div>
<a name="fusion.sequence.intrinsic.metafunctions.empty.expression_semantics"></a><h6>
<a name="id507195"></a>
<a href="empty.html#fusion.sequence.intrinsic.metafunctions.empty.expression_semantics">Expression
Semantics</a>
</h6>
<pre class="programlisting">
<span class="identifier">result_of</span><span class="special">::</span><span class="identifier">empty</span><span class="special">&lt;</span><span class="identifier">Seq</span><span class="special">&gt;::</span><span class="identifier">type</span>
</pre>
<p>
<span class="bold"><b>Return type</b></span>: An <a href="http://www.boost.org/libs/mpl/doc/refmanual/integral-constant.html" target="_top">MPL
Integral Constant</a>
</p>
<p>
<span class="bold"><b>Semantics</b></span>: Returns <tt class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></tt>
if <tt class="computeroutput"><span class="identifier">Seq</span></tt> has zero elements,
<tt class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">false_</span></tt> otherwise.
</p>
<p>
/sequence/intrinsic/empty.hpp&gt;
</p>
<a name="fusion.sequence.intrinsic.metafunctions.empty.example"></a><h6>
<a name="id507356"></a>
<a href="empty.html#fusion.sequence.intrinsic.metafunctions.empty.example">Example</a>
</h6>
<pre class="programlisting">
<span class="keyword">typedef</span> <a href="../../../container/vector.html" title="vector"><tt class="computeroutput"><span class="identifier">vector</span></tt></a><span class="special">&lt;&gt;</span> <span class="identifier">empty_vec</span><span class="special">;</span>
<span class="keyword">typedef</span> <a href="../../../container/vector.html" title="vector"><tt class="computeroutput"><span class="identifier">vector</span></tt></a><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span><span class="keyword">float</span><span class="special">,</span><span class="keyword">char</span><span class="special">&gt;</span> <span class="identifier">vec</span><span class="special">;</span>
<span class="identifier">BOOST_MPL_ASSERT</span><span class="special">((</span><a href="empty.html" title="empty"><tt class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">empty</span></tt></a><span class="special">&lt;</span><span class="identifier">empty_vec</span><span class="special">&gt;));</span>
<span class="identifier">BOOST_MPL_ASSERT_NOT</span><span class="special">((</span><a href="empty.html" title="empty"><tt class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">empty</span></tt></a><span class="special">&lt;</span><span class="identifier">vec</span><span class="special">&gt;));</span>
</pre>
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